Methods of forming capacitors

ABSTRACT

In one aspect, the invention encompasses a method of forming a capacitor. A mass is formed over an electrical node. An opening is formed within the mass. The opening has a lower portion proximate the node and an upper portion above the lower portion. The lower portion is wider than the upper portion. A first conductive layer is formed within the opening and along a periphery of the opening. After the first conductive layer is formed, a portion of the mass is removed from beside the upper portion of the opening while another portion of the mass is left beside the lower portion of the opening. A dielectric material is formed over the first conductive layer, and a second conductive layer is formed over the dielectric material. The second conductive layer is separated from the first conductive layer by the dielectric material. In another aspect, the invention encompasses a capacitor construction.

TECHNICAL FIELD

The invention pertains to capacitor constructions and methods of formingcapacitors. In a particular aspect, the invention pertains to crowncapacitor constructions.

BACKGROUND OF THE INVENTION

A method of forming a prior art crown capacitor construction isdescribed with reference to FIGS. 1 and 2. Referring to FIG. 1, asemiconductive material wafer fragment 10 comprises a substrate 12 whichsupports an electrical node 14. Substrate 12 can comprise, for example,lightly doped monocrystalline silicon. Electrical node 14 can comprise,for example, a conductively-doped diffusion region provided within amonocrystalline silicon substrate 12.

To aid in interpretation of the claims that follow, the terms“semiconductive substrate” and “semiconductor substrate” are defined tomean any construction comprising semiconductive material, including, butnot limited to, bulk semiconductive materials such as a semiconductivewafer (either alone or in assemblies comprising other materialsthereon), and semiconductive material layers (either alone or inassemblies comprising other materials). The term “substrate” refers toany supporting structure, including, but not limited to, thesemiconductive substrates described above.

An insulative layer 16 is formed over substrate 12. Insulative layer 16can comprise, for example, silicon dioxide, silicon nitride,borophosphosilicate glass (BPSG), or phosphosilicate glass (PSG). Layer16 has an opening 18 extending therethrough to electrical node 14. Aconductive plug 20 is provided within opening 18. Conductive plug 20 cancomprise, for example, a metal, or conductively doped polysilicon.

A container-shaped storage node 22 is provided over insulative layer 16,and over conductive plug 18. Storage node 22 is in electrical connectionwith electrical node 14 through conductive plug 18. Container-shapedstorage node 22 can also be referred to as a crown-shaped storage node.Storage node 22 comprises upwardly extending members 21, and ahorizontally extending member 23.

Referring to FIG. 2, a dielectric material 24 is provided over storagenode 22, and a second capacitor electrode layer 26 is provided overdielectric material 24. Dielectric material 24 can comprise, forexample, a combination of silicon dioxide and silicon nitride.Alternatively, dielectric material 24 can comprise tantalum pentoxide.Second capacitor electrode 26 can comprise, for example, a metal,conductively doped polysilicon, or a metal-comprising compound, such as,for example, titanium nitride.

Storage node 22, dielectric material 24, and second capacitor electrode26, together define a crown capacitor.

A problem with the processing described above with reference to FIGS. 1and 2 is that the upwardly extending members 21 of storage node 22 canbe easily broken during subsequent processing. It would therefore bedesirable to develop alternative methods of forming crown capacitors.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses a method of forming acapacitor. A mass is formed over an electrical node. An opening isformed within the mass. The opening has a lower portion proximate thenode and an upper portion above the lower portion. The lower portion iswider than the upper portion. A first conductive layer is formed withinthe opening and along a periphery of the opening. After the firstconductive layer is formed, a portion of the mass is removed from besidethe upper portion of the opening while another portion of the mass isleft beside the lower portion of the opening. A dielectric material isformed over the first conductive layer, and a second conductive layer isformed over the dielectric material. The second conductive layer isseparated from the first conductive layer by the dielectric material.

In another aspect, the invention encompasses a capacitor construction.Such construction includes an insulative mass over an electrical node,and an opening extending through the mass to the electrical node. Theconstruction further includes a storage node layer within the opening.The storage node layer extends around a periphery of the opening andprotrudes above the insulative mass. The storage node layer defines acontainer shape having a void extending therein. The void has a lowerportion within the opening and an upper portion above the opening. Theupper portion of the void is narrower than the lower portion.Additionally, the construction includes a dielectric material within thevoid and partially filling the void, and a second capacitor electrodewithin the void and separated from the first conductive layer by thedielectric material.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of a semiconductivematerial wafer fragment shown at a preliminary step of a prior artcapacitor-forming process.

FIG. 2 is a view of the FIG. 1 wafer fragment shown at a prior artprocessing step subsequent to that of FIG. 1.

FIG. 3 is a diagrammatic, cross-sectional view of a semiconductivematerial wafer fragment shown at a preliminary step of acapacitor-forming method encompassed by the present invention.

FIG. 4 is a view of the FIG. 3 wafer fragment shown at a processing stepsubsequent to that of FIG. 3.

FIG. 5 is a view of the FIG. 3 wafer fragment shown at a processing stepsubsequent to that of FIG. 4.

FIG. 6 is a view of the FIG. 3 wafer fragment shown at a processing stepsubsequent to that of FIG. 5.

FIG. 7 is a view of the FIG. 3 wafer fragment shown at a processing stepsubsequent to that of FIG. 6.

FIG. 8 is a view of the FIG. 3 wafer fragment shown at a processing stepsubsequent to that of FIG. 7.

FIG. 9 is a top view of the FIG. 8 wafer fragment.

FIG. 10 is a view of the FIG. 3 wafer fragment shown at a processingstep subsequent to that of FIG. 8.

FIG. 11 is a view of the FIG. 3 wafer fragment shown at a secondembodiment processing step subsequent to that of FIG. 5.

FIG. 12 is a view of the FIG. 3 wafer fragment shown at a processingstep in accordance with the second embodiment and subsequent to that ofFIG. 11.

FIG. 13 is a top view of the FIG. 12 wafer fragment.

FIG. 14 is a view of the FIG. 3 wafer fragment shown at a processingstep in accordance with the second embodiment and subsequent to that ofFIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

A first embodiment method of forming a capacitor construction inaccordance with the present invention is described with reference toFIGS. 3-10. Referring to FIG. 3, a semiconductive material waferfragment 50 is shown at a preliminary process step. Wafer fragment 50comprises a substrate 52 supporting an electrical node 54. Substrate 52and node 54 can comprise, for example, the constructions described abovefor substrate 12 and node 14, respectively, of the prior artconstruction of FIG. 1. Substrate 52 and node 54 can also, of course,comprise alternate constructions.

An insulative material 56 is formed over substrate 52. Insulativematerial 56 can comprise, for example, materials similar to thosedescribed above with reference to insulative layer 16 of the prior artconstruction of FIG. 1. An opening 58 extends through insulativematerial 56, and a conductive material 60 is formed within the opening.Conductive material 60 can comprise, for example, constructions similarto those discussed above with reference to conductive plug 20 of theprior art construction of FIG. 1. Plug 60 can also comprise alternateconstructions. It is noted that although the term “electrical node” was4 utilized above in describing node 54, plug 60 can also be referred toas an “electrical node”.

A mass 62 is formed over insulative layer 56 and electrical node 60. Inthe shown embodiment, mass 62 comprises the three distinct layers 64, 66and 68. Layers 64, 66 and 68 preferably comprise materials selectivelyetchable relative to one another. For instance, in one embodiment layer64 consists essentially of PSG, layer 66 consists essentially of siliconnitride, and layer 68 consists essentially of BPSG. In anotherembodiment, layer 64 consists essentially of doped silicon dioxide,layer 66 consists essentially of silicon nitride, and layer 68 consistsessentially of undoped silicon dioxide. Layers 64 and 66 are preferablyelectrically insulative. Layers 64, 66 and 68 can be formed tothicknesses of, for example, about 100 nanometers, 10 nanometers and 400nanometers, respectively.

Referring to FIG. 4, an opening 70 is etched through layers 64, 66 and68 to expose node 60. Such opening can be formed by, for example,photolithographic processing to form a patterned photoresist mask (notshown) over layer 68, and subsequently utilizing an etchant comprising ahalogenated-hydro-carbon and inert gases to etch through layers 64, 66,and 68 in the location of opening 70.

Referring to FIG. 5, the material of layer 64 is etched faster than thematerials of layers 66 and 68. Such faster etching can be accomplishedfor an etch selective for the material of layer 64 relative to thematerials of layers 66 and 68. In embodiments wherein the material oflayer 64 comprises PSG, and the materials of layer 66 and 68 comprisesilicon nitride and BPSG, respectively, the selective etching can beaccomplished utilizing hydrofluoric acid. Also, in embodiments in whichlayer 64 comprises doped silicon dioxide, and layers 66 and 68 comprisesilicon nitride and undoped silicon dioxide, respectively, the selectiveetching can be accomplished utilizing hydrofluoric acid. It is notedthat a hydrofluoric acid etch would typically be done prior to formationof a storage node in contact with electrical node 60 (the storage nodeis described below with reference to FIGS. 6-10), to clean exposedportions of fragment 50 prior to formation of the storage node.Accordingly, the etching with hydrofluoric acid does not add anadditional process step beyond the steps generally utilized forcapacitor fabrication.

Is After the etching of layer 64, opening 70 comprises two distinctportions, labeled as portions 72 and 74 in FIG. 5. Portion 72 is a lowerportion, and portion 74 is an upper portion. Portions 72 and 74 join ata lower edge of layer 66. Lower portion 72 has a width “Y” and upperportion 74 has a width “Z”, with “Z” being less than “Y”.

Referring to FIG. 6, a first conductive layer 80 is formed over mass 62and within opening 70. First conductive layer 80 can comprise, forexample, conductively doped polysilicon and/or a metal. First conductivelayer 80 preferably comprises conductively doped roughened polysilicon,such as, for example, conductively doped hemispherical grainpolysilicon. First conductive layer 80 only partially fills opening 70and defines a void 86 therein.

A masking material 82 is formed over conductive layer 80. Maskingmaterial 82 is preferably applied while wafer 50 is spinning, andapplied at a viscosity such that material 82 flows into opening 70.Further, material 82 is preferably applied to a thickness such thatopening 70 is predominantly filled, but only a very thin amount ofmaterial 82 is over mass 62. Material 82 can comprise, for example, 14photoresist.

Referring to FIG. 7, wafer fragment 50 is subjected to etchingconditions which remove the thin layer of masking material 82 from overmass 62, and subsequently remove first conductive layer 80 from overmass 62. During such etching, the portion of masking material 82 withinopening 70 protects first conductive layer 80 within opening 70.Accordingly, the etching forms first conductive layer 80 into acontainer-shape retained within opening 70. The container-shape can alsobe referred to as a crown-shape.

The methodologies of FIGS. 6 and 7 are but one exemplary method ofremoving conductive material 80 from over mass 62 while leaving some ofconductive material 80 within opening 70, and other methods will berecognized by persons of ordinary skill in the art. For instance,alternative methods of removing conductive material 80 from over mass 62include chemical-mechanical polishing and resist etch-back.

Referring to FIG. 8, wafer fragment 50 is subjected to conditions whichremove masking material 82 from within opening 70. In exemplaryembodiments where a mask material 82 comprises photoresist, suchconditions can comprise exposure to oxygen and heat sufficient to ashphotoresist 82. Also, wafer fragment 50 is subjected to conditions whichremove layer 68 from over layer 66. In preferred embodiments whereinlayer 68 is selectively etchable relative to layer 66, layer 66constitutes an etch-stop. In an exemplary embodiment wherein layer 68comprises undoped silicon oxide and layer 66 comprises silicon nitride,the selective etching of layer 68 relative to layer 66 can beaccomplished utilizing hydrofluoric acid. The removal of layer 68reduces a height of mass 62. The removal of layer 68 increases thesurface of the conductive material.

FIG. 9 shows a top view of the fragment 50 of FIG. 8, and shows thatconductive material 80 is preferably in a container-shape comprising acircular opening 86 extending therein.

Referring to FIG. 10, dielectric material 90, and a second conductivelayer 92 are formed over first conductive layer 80 and within void 86.Dielectric material 90 and second conductive material 92 can comprise,for example, materials similar to those discussed above regardingdielectric material 24 and conductive material 26, respectively, of theprior art (FIG. 2). First conductive material 80, dielectric layer 90,and second conductive layer 92 together define a capacitor, with firstconductive material 80 corresponding to a storage node of the capacitorand second conductive material 92 corresponding to a second capacitorelectrode. Second capacitor electrode 92 is separated from storage node80 by dielectric layer 90.

In the shown embodiment, a portion of storage node 80 is within mass 62,and a portion extends above mass 62. Accordingly, storage node 80corresponds to a partially buried storage node. Storage node 80, likeprior art storage node 22, comprises upwardly projecting 14 portions(labeled as 100 for storage node 80), and a horizontal portion (labeledas 102 for storage node 80). However, the partially buried nature ofcapacitor 80 provides structural support for vertically extendingportions 100 beyond that provided for vertically extending portions 21(FIG. 2) of a prior art capacitor construction achieving a samecapacitance as the capacitor construction of FIG. 10. Such structuralsupport can increase a mechanical stability of vertically projectingportions 100 relative to vertically projecting portions 21. Also, thepartially-buried nature of a storage node of the present inventionreduces a non-planarity across an upper surface of wafer fragment 50 inthe processing steps of FIGS. 8-10 relative to the non-planarityassociated with an upper surface of wafer fragment 50 in prior artprocessing steps associated with FIGS. 1 and 2. Such reduction innon-planarity can alleviate problems associated with photolithographicprocessing. Specifically, photolithographic processing becomesincreasingly more complicated with increasing non-planarity across anupper surface that is to be patterned.

A second embodiment of the present invention is described with referenceto FIGS. 11-14. In referring to FIGS. 11-14, similar numbering will beused as was utilized above in describing the first embodiments of FIGS.3-10, with the suffix “a” indicating structures associated with FIGS.11-14.

Referring to FIG. 11, a semiconductive material wafer fragment 50 a isillustrated at a processing step subsequent to the step illustrated inFIG. 5. Wafer fragment 50 a comprises a first conductive material 80 aformed over a mass 62 a and within an opening 70 a. Conductive material80 a only partially fills opening 70 a, and accordingly defines a void86 a therein. Mass 62 a comprises layers 64 a, 66 a and 68 a.

A masking material 82 a is formed within void 86 a and over mass 62 a,and patterned to cover only a portion of conductive material 80 a overmass 62 a. Masking material 82 a can comprise, for example, photoresist,and can be patterned by, for example, photolithographic processing.

Referring to FIG. 12, wafer fragment 50 a is subjected to etchingconditions which remove exposed portions of conductive material 80 afrom over mass 62 a. Subsequently, masking material 82 a (FIG. 11) isremoved from within void 86 a. In the shown embodiment, a portion ofconductive material 80 a remains over mass 62 a. Such portion defines aflange 150. A top view of the construction of FIG. 12 is shown in FIG.13. As can be seen in such top view, flange 150 extends around an upperperiphery of a storage node defined by layer 80 a.

Referring to FIG. 14, layer 68 a (FIG. 12) is removed. Subsequently, adielectric material 90 a and a second conductive layer 92 a are formedover storage node 80 a and within void 86 a to form a capacitorconstruction analogous to the construction described above withreference to FIG. 10.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A method of forming a capacitor, comprising:forming a mass over an electrical node; forming an opening within themass, the opening having a lower portion proximate the node and an upperportion above the lower portion, the lower portion being wider than theupper portion; forming a first conductive layer within the opening andalong a periphery of the opening; after forming the first conductivelayer, removing a portion of the mass from beside the upper portion ofthe opening while leaving an other portion of the mass beside the lowerportion of the opening; forming a dielectric material over the firstconductive layer; forming a second conductive layer over the dielectricmaterial, the second conductive layer being separated from the firstconductive layer by the dielectric material; and wherein the forming thefirst conductive material comprises: depositing polysilicon within theopening and over the mass; forming photoresist within the opening toprotect the polysilicon within the opening; exposing at least some ofthe polysilicon which is not within the opening to etching conditions toremove said at least some of the polysilicon; and ashing the photoresistto remove the photoresist from within the opening.
 2. A method offorming a capacitor, comprising: forming a first layer over anelectrical node; forming a second layer over the first layer; forming anopening through the first and second layers; after forming the opening,exposing the first and second layers to etching conditions which etchthe first layer faster than the second layer, the exposing widening alowest-most portion of the opening relative to an upper portion of theopening; forming a first conductive layer within the opening; afterforming the first conductive layer, removing the second layer whileleaving the first layer; forming a dielectric material over the firstconductive layer; and forming a second conductive layer over thedielectric material, the second conductive layer being separated fromthe first conductive layer by the dielectric material.
 3. The method ofclaim 2 wherein the second layer consists essentially of an insulativematerial.
 4. The method of claim 2 wherein the first layer consistsessentially of a first material, and wherein the second layer consistsessentially of a second material, the first material being selectivelyetchable relative to the second material.
 5. The method of claim 4wherein the first material is doped silicon dioxide and the secondmaterial is undoped silicon dioxide, and wherein the selectively etchingcomprises etching with HF.
 6. The method of claim 4 wherein the firstmaterial is PSG and the second material is BPSG, and wherein theselectively etching comprises etching with HF.
 7. The method of claim 2wherein the first conductive layer comprises roughened polysilicon. 8.The method of claim 2 wherein the forming the first conductive layercomprises: depositing polysilicon within the opening and over the secondlayer; and removing at least some of the polysilicon from over thesecond layer.
 9. A method of forming a capacitor, comprising: forming afirst layer over an electrical node; forming a second layer over thefirst layer; forming an opening through the first and second layers;after forming the opening, exposing the first and second layers toetching conditions which etch the first layer faster than the secondlayer, the exposing widening a lower portion of the opening relative toan upper portion of the opening; forming a first conductive layer withinthe opening; after forming the first conductive layer, removing thesecond layer while leaving the first layer; forming a dielectricmaterial over the first conductive layer; forming a second conductivelayer over the dielectric material, the second conductive layer beingseparated from the first conductive layer by the dielectric material;and wherein the forming the first conductive layer comprises: depositingpolysilicon within the opening and over the second layer; formingphotoresist within the opening to protect the polysilicon within theopening; exposing at least some of the polysilicon which is not withinthe opening to etching conditions to remove said at least some of thepolysilicon; and ashing the photoresist to remove the photoresist fromwithin the opening.
 10. A method of forming a capacitor, comprising:forming a first insulative layer over an electrical node; forming asecond insulative layer over the first insulative layer; forming a thirdinsulative layer over the second insulative layer; forming an openingthrough the first, second and third insulative layers; after forming theopening, exposing the first, second and third layers to etchingconditions which etch the first insulative layer faster than the secondand third layers, the exposing widening a lowest-most portion of theopening relative to an upper portion of the opening; forming a firstconductive layer within the opening; after forming the first conductivelayer, removing the third insulative layer while leaving the first andsecond insulative layers; forming a dielectric material over the firstconductive layer; and forming a second conductive layer over thedielectric material, the second conductive layer being separated fromthe first conductive layer by the dielectric material.
 11. The method ofclaim 10 wherein the first insulative layer consists essentially of afirst material, the second insulative layer consists essentially of asecond material, and the third insulative layer consists essentially ofa third material, the first material being selectively etchable relativeto the second material and third materials, the third material beingselectively etchable relative to the second material.
 12. The method ofclaim 11 wherein the first material is doped silicon dioxide, the secondmaterial is silicon nitride, and the third material is undoped silicondioxide, wherein the selectively etching the first material relative tothe second and third materials comprises etching with HF.
 13. The methodof claim 11 wherein the first material is PSG, the second material issilicon nitride, and the third material is BPSG, wherein the selectivelyetching the first material relative to the second and third materialscomprises etching with HF.
 14. The method of claim 11 wherein the firstconductive layer comprises roughened polysilicon.
 15. The method ofclaim 11 wherein the forming the first conductive layer comprises:depositing polysilicon within the opening and over the third insulativelayer; and removing at least some of the polysilicon from over the thirdinsulative layer.
 16. A method of forming a capacitor, comprising:forming a first insulative layer over an electrical node; forming asecond insulative layer over the first insulative layer; forming a thirdinsulative layer over the second insulative layer; forming an openingthrough the first, second and third insulative layers; after forming theopening, exposing the first, second and third layers to etchingconditions which etch the first insulative layer faster than the secondand third layers, the exposing widening a lower portion of the openingrelative to an upper portion of the opening; forming a first conductivelayer within the opening; after forming the first conductive layer,removing the third insulative layer while leaving the first and secondinsulative layers; forming a dielectric material over the firstconductive layer; forming a second conductive layer over the dielectricmaterial, the second conductive layer being separated from the firstconductive layer by the dielectric material; and wherein the forming thefirst conductive layer comprises: depositing polysilicon within theopening and over the third insulative layer; forming photoresist withinthe opening to protect the polysilicon within the opening; exposing atleast some of the polysilicon which is not within the opening to etchingconditions to remove said at least some of the polysilicon; and ashingthe photoresist to remove the photoresist from within the opening.